U.S. patent number 7,078,850 [Application Number 10/894,420] was granted by the patent office on 2006-07-18 for piezoelectric power generation device and piezoelectric ceramics member used therefor.
This patent grant is currently assigned to USC Corporation. Invention is credited to Yasuhiro Sakai.
United States Patent |
7,078,850 |
Sakai |
July 18, 2006 |
Piezoelectric power generation device and piezoelectric ceramics
member used therefor
Abstract
In a piezoelectric power generation device and a piezoelectric
ceramics member used in the device excellent in its power
generation efficiency in which the polarization of piezoelectric
ceramics elements is set to the same direction and an extremely
thin metallic electrode is sandwiched in between the piezoelectric
ceramics elements so that a current output obtained in the
piezoelectric power generation device can be improved substantially
to about two times as high as a current output obtained by a usual
piezoelectric power generation device and the parasitic resonance
of the electrode can be prevented, the piezoelectric power
generation device generates power by applying a distortion
deformation to piezoelectric ceramics members formed in plate
shapes. The piezoelectric power generation device includes the
piezoelectric ceramics members each having the two plate shaped
piezoelectric ceramics elements whose polarization is set to the
same direction and the extremely thin metallic electrode interposed
between the piezoelectric ceramics elements, the piezoelectric
ceramics member being formed in a laminar shape by uniting the
piezoelectric ceramics elements through the metallic electrode; and
the cushion materials for supporting central parts or both end
parts of one surfaces of the piezoelectric ceramics members. Thus,
the piezoelectric power generation device has a soft support
structure in which the natural oscillation of the piezoelectric
ceramics members is hardly transmitted to other structural members.
A step part is formed in the piezoelectric ceramics member and the
metallic electrode.
Inventors: |
Sakai; Yasuhiro (Tokyo,
JP) |
Assignee: |
USC Corporation (Tokyp,
JP)
|
Family
ID: |
35656397 |
Appl.
No.: |
10/894,420 |
Filed: |
July 20, 2004 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20060017353 A1 |
Jan 26, 2006 |
|
Current U.S.
Class: |
310/339; 310/329;
310/332 |
Current CPC
Class: |
H01L
41/113 (20130101); H02N 2/183 (20130101) |
Current International
Class: |
H01L
41/08 (20060101) |
Field of
Search: |
;310/329-332,339,345 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Budd; Mark
Attorney, Agent or Firm: Armstrong. Kratz, Quintos, Hanson
& Brooks, LLP
Claims
What is claimed is:
1. A piezoelectric power generation device for generating power by
applying distortion deformation to piezoelectric ceramics members
formed in plate shapes, said piezoelectric power generation device
comprising: two plate shaped piezoelectric ceramics elements
included in each of the piezoelectric ceramics members whose
polarization is set to the same direction and an extremely thin
metallic electrode interposed between the piezoelectric ceramics
elements, the piezoelectric ceramics member being formed in a
laminar shape by uniting the piezoelectric ceramics elements to the
metallic electrode; and cushion materials for supporting central
parts or both end parts of one surfaces of the piezoelectric
ceramics members, wherein the piezoelectric power generation device
has a soft support structure in which the natural oscillation of
the piezoelectric ceramics members is hardly transmitted to other
structural members, wherein the piezoelectric ceramics member is
formed by forming the two piezoelectric ceramics elements in the
same configuration, and wherein both the end parts of the two
piezoelectric ceramics elements are arranged uniformly, the
metallic electrode protrudes from one end part of both the
piezoelectric ceramics elements, the lead wire is connected to the
protruding part, and then, the protruding part is embedded in an
adhesive to be formed integrally with the piezoelectric ceramics
elements.
2. The piezoelectric power generation device according to claim 1,
the piezoelectric ceramics members supported by the cushion
materials are opposed to each other and a hard striking member is
provided between both the piezoelectric ceramics members which
reciprocates between both the piezoelectric ceramics members to
strike each piezoelectric ceramics member.
3. The piezoelectric power generation device according to claim 1,
wherein a hard striking member is disposed in one or both sides of
the piezoelectric ceramics members supported by the cushion
materials, which reciprocates between the piezoelectric ceramics
members to strike the piezoelectric ceramics members.
4. The piezoelectric ceramics member according to claim 1, wherein
the two piezoelectric ceramics elements are respectively formed by
uniting and laminating a plurality of sheets.
5. The piezoelectric ceramics member according to claim 1, wherein
lead zirconate titanate based material is used as the piezoelectric
ceramics elements.
6. The piezoelectric ceramics member according to claim 1, wherein
the metallic electrode is made of electrically conductive metal
such as phosphor bronze or brass.
7. The piezoelectric ceramics member according to claim 2, wherein
the piezoelectric ceramics member is formed by forming the two
piezoelectric ceramics elements in the same configuration.
8. The piezoelectric ceramics member according to claim 3, wherein
the piezoelectric ceramics member is formed by forming the two
piezoelectric ceramics elements in the same configuration.
9. The piezoelectric ceramics member according to claim 7, wherein
the two piezoelectric ceramics elements are respectively formed by
uniting and laminating a plurality of sheets.
10. The piezoelectric ceramics member according to claim 8, wherein
the two piezoelectric ceramics elements are respectively formed by
uniting and laminating a plurality of sheets.
11. The piezoelectric ceramics member according to claim 7, wherein
lead zirconate titanate based material is used as the piezoelectric
ceramics elements.
12. The piezoelectric ceramics member according to claim 8, wherein
lead zirconate titanate based material is used as the piezoelectric
ceramics elements.
13. The piezoelectric ceramics member according to claim 7, wherein
the metallic electrode is made of electrically conductive metal
such as phosphor bronze or brass.
14. The piezoelectric ceramics member according to claim 8, wherein
the metallic electrode is made of electrically conductive metal
such as phosphor bronze or brass.
15. The piezoelectric ceramics member according to claim 7, wherein
the two piezoelectric ceramics elements are arranged uniformly in
one end side, and, the other piezoelectric ceramics element is
formed longer than one piezoelectric ceramics element in the other
end side to form a step part, and a lead wire connecting end part
of the metallic electrode is extended to the step part.
16. The piezoelectric ceramics member according to claim 8, wherein
the two piezoelectric ceramics elements are arranged uniformly in
one end side, and, the other piezoelectric ceramics element is
formed longer than one piezoelectric ceramics element in the other
end side to form a step part, and a lead wire connecting end part
of the metallic electrode is extended to the step part.
17. The piezoelectric ceramics member according to claim 7, wherein
both the end parts of the two piezoelectric ceramics elements are
arranged uniformly, the metallic electrode protrudes from one end
part of both the piezoelectric ceramics elements, the lead wire is
connected to the protruding part, and then, the protruding part is
embedded in an adhesive to be formed integrally with the
piezoelectric ceramics elements.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric power generation
device that can obtain output current substantially two times as
much as that of a piezoelectric power generation device using a
usual piezoelectric ceramics element and can prevent the parasitic
resonance of a metal electrode.
2. Description of the Related Art
A piezoelectric material has various application aspects as a
converting element between mechanical energy and electrical energy.
As materials showing a piezoelectric effect, many materials of both
inorganic materials and organic materials are well-known. As
materials that are currently put to practical use, materials such
as a PZT type ceramics (piezoelectric ceramics) are
exemplified.
The piezoelectric ceramics element is an element provided with
piezoelectric characteristics formed in such a way that high DC
voltage is applied to a polycrystalline material to generate
remanence. Because a basic piezoelectric constant can be relatively
freely changed depending on the composition of the piezoelectric
ceramics element, a use thereof is wide. Especially, the
piezoelectric ceramics element composed of lead zirconate titanate
(PZT) has a wide selection range of composition ratio or additives
and a variety of application ranges.
FIG. 7 is an explanatory view of a usual piezoelectric power
generation device. The piezoelectric power generation device is
formed by uniting a piezoelectric ceramics element plate 31 to a
base 32 made of an acrylic material and fixing both the end parts
of the base 32 by holders 33 made of a hard material such as metal.
Then, a steel ball 35 is dropped on the ceramics element plate 31
to apply mechanical impact energy due to a collision to the
piezoelectric element plate 31, excite a flexural oscillation on
the piezoelectric element plate 31 including the base 32 and take
out electric energy.
However, although the practicability of the usual PZT type
piezoelectric ceramics element is anticipated, a quantity of
generated energy is very small. Thus, the usual PZT type
piezoelectric ceramics element is undesirably deficient in its
practicability for the piezoelectric power generation device. In
the power generation device using the piezoelectric ceramics
element of this type, the natural oscillation of the piezoelectric
ceramics element plate 31 essentially needs to be continued as long
as possible. Therefore, a support structure needs to be realized
that the natural oscillation of the piezoelectric ceramics element
plate 31 does not accompany a mechanical resistance. Further, in
the above-described related art, because the material of the base
32 is different from the material of the piezoelectric ceramics
element plate 31, a center of oscillation (a part that does not
expand and contract) is hardly disposed on a uniting surface of the
base 32 and the piezoelectric ceramics element plate 31. When the
center appears in the piezoelectric ceramics element plate 31, a
cancellation in a polarization is undesirably generated to lower
power generation efficiency.
In order to solve the above-described problems of the usual power
generation device, the applicant of the present invention
previously proposes a piezoelectric power generation device
(disclosed in Japanese Patent Application Laid-Open No.
2001-145375) shown in FIG. 8. In this piezoelectric power
generation device, two plate shaped piezoelectric ceramics elements
1a and 1b are united to each other with polarization set to
opposite directions to form laminar piezoelectric ceramics members
1 (PZT1) and 1 (PZT2). Then, one surface of each of the
piezoelectric ceramics members 1 and 1 is struck to generate power.
Thus, the power generation device good in its power generation
efficiency and effective in small power generation is obtained.
It is a first object of the present invention to provide a
piezoelectric power generation device excellent in its power
generation efficiency in which polarization is set to the same
direction differently from the previous application and an
extremely thin metal electrode is sandwiched between piezoelectric
ceramics elements so that a current output obtained in the
piezoelectric power generation device with the above-described
structure previously filed by the applicant of the present
invention can be improved substantially to about twice as high as
the previous current output.
It is a second object of the present invention to provide a
piezoelectric power generation device that can greatly improve
power generation efficiency by forming different level parts in a
piezoelectric ceramics member and a metal electrode to eliminate a
parasitic resonance in the piezoelectric power generation
device.
SUMMARY OF THE INVENTION
In order achieve the above-described objects, a piezoelectric power
generation device according to the present invention generates
power by applying a distortion deformation to piezoelectric
ceramics members 10 formed in plate shapes. Each of the
piezoelectric ceramics members is formed by two plate shaped
piezoelectric ceramics elements 10a and 10b whose polarization is
set to the same direction and an extremely thin metallic electrode
11 interposed between the piezoelectric ceramics elements 10a and
10b. The piezoelectric ceramics member is formed in a laminar shape
by uniting the piezoelectric ceramics elements through the metallic
electrode 11. Cushion materials 3 support central parts or both end
parts of one surfaces of the piezoelectric ceramics members 10. The
piezoelectric power generation device has a soft support structure
in which the natural oscillation of the piezoelectric ceramics
members 10 is hardly transmitted to other structural members.
Further, in order to achieve the above-described objects, in the
piezoelectric power generation device according to the present
invention, the piezoelectric ceramics members 10 supported by the
cushion materials 3 and 3 are opposed to each other and a hard
striking member 4 is provided which reciprocates between both the
piezoelectric ceramics members 10 and 10 to strike each
piezoelectric ceramics member 10.
Further, according to the present invention, a hard striking member
4 is disposed in one or both sides of the piezoelectric ceramics
members 10 and 10 supported by the cushion materials 3 and 3, which
reciprocates between the piezoelectric ceramics members 10 to
strike each piezoelectric ceramics member 10.
The piezoelectric ceramics member 10 used in the piezoelectric
power generation device constructed as described above is obtained
by forming the two piezoelectric ceramics elements 10a and 10b in
the same configuration so that stable power generation efficiency
can be obtained.
Further, in the present invention, the two piezoelectric ceramics
elements 10a and 10b are respectively formed by uniting and
laminating a plurality of sheets as described above.
In this case, a lead zirconate titanate material is used for the
piezoelectric ceramics elements 10a and 10b to greatly improve a
power generation efficiency.
Further, the metallic electrode 11 is made of electrically
conductive metal such as phosphor bronze or brass. The thickness of
the metallic electrode is desirably set to, for instance, 10 .mu.m
to 50 .mu.m and may be set to 0.5 to 1 mm or longer when the
oscillation of the electrode 11 can be suppressed to a low
level.
Further, in the present invention, the two piezoelectric ceramics
elements 10a and 10b are arranged uniformly in one end side, and,
the end part 10a1 or 10b1 of one piezoelectric ceramics element 10a
or 10b is formed longer than the other in the other side to form a
step part 10a1 or 10b1, and a lead wire connecting end part 11A of
the metallic electrode 11 is extended to the step part 10a1 or
10b1.
Further, in the present invention, both the end parts of the two
piezoelectric ceramics elements 10a and 10b are arranged uniformly,
the metallic electrode 11 protrudes outward from one end part of
both the piezoelectric ceramics elements 10a and 10b, a lead wire
9C is connected to the protruding part 11A, and then, the
protruding part 11A is embedded in an adhesive to be formed
integrally with the piezoelectric ceramics elements 10a and 10b.
Thus, the protruding part 11A of the metallic electrode 11 is
prevented from having an oscillation different from the oscillation
of the piezoelectric ceramics elements 10a and 10b.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an explanatory view showing a piezoelectric power
generation device according to an embodiment of the present
invention.
FIG. 2 is a circuit diagram of a charging device for the
piezoelectric power generation device.
FIG. 3 is an explanatory side view showing a model of an original
form of a piezoelectric ceramics member used in the present
invention.
FIG. 4 is a perspective view showing an embodiment of the
piezoelectric ceramics member.
FIG. 5 is a side view of the piezoelectric ceramics member.
FIGS. 6A and 6B are explanatory plan views respectively showing
alternative examples of an embodiment A of a piezoelectric ceramics
member. FIGS. 6C and 6D are explanatory plan views respectively
showing alternative examples of an embodiment B of a piezoelectric
ceramics member.
FIG. 7 is an explanatory view of a usual piezoelectric power
generation device.
FIG. 8 is an explanatory view of a piezoelectric power generation
device previously proposed by the applicant of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, the present invention will be described in detail on the basis
of embodiments shown in the accompanying drawings.
In a power generation device shown in FIG. 1, piezoelectric
ceramics members 10 are arranged at both end sides of a tubular
vessel 8 with both ends closed and the piezoelectric ceramics
members 10 are struck by a steel ball 4 to generate power.
To one side surface of the vessel 8, a cushion member 3 is bonded
by using an adhesive 6. Only to the central part of the cushion
member 3, the piezoelectric ceramics member 10 is bonded by using
an adhesive 5. To the other side surface of the vessel 8, the
piezoelectric ceramics member 10 is bonded in the same manner as
described above and both the piezoelectric ceramics members 10 are
opposed to each other.
Protector plates 2 are fixed to the central parts on the opposed
surfaces of the piezoelectric ceramics members 10. Then, a pipe 7
is disposed between both the piezoelectric ceramics members 10 and
the steel ball 4 is provided in the pipe 7 to freely roll.
In the present invention, for instance, when the piezoelectric
ceramics members 10 are horizontally arranged, not only the central
parts, but also both the end parts of the piezoelectric ceramics
members 10 may be held by the cushion members 3. Otherwise, the
central parts and both the end parts of the piezoelectric ceramics
members may be supported by the cushion members 3 and their
supporting parts may be arranged and held in the upper and lower
surfaces of the piezoelectric ceramics members 10.
The piezoelectric ceramics members 10 respectively include two
plate shaped piezoelectric ceramics elements 10a and 10b having the
same form (the same material, the same shape and the same
thickness). The polarity of polarization of each of the
piezoelectric ceramics elements 10a and 10b has the same direction.
Between the piezoelectric ceramics elements 10a and 10b, an
extremely thin metallic electrode 11 made of electrically
conductive metal such as phosphor bronze or brass and having the
thickness of 10 .mu.m to 50 .mu.m is disposed. The piezoelectric
ceramics member 10 is formed by connecting the piezoelectric
ceramics elements 10a and 10b to the metallic electrode 11.
According to the present invention, it is to be understood that the
thickness of the metallic electrode 11 is not limited to the
above-described example, and, for instance, the thickness of the
metallic electrode may be 0.5 mm or longer.
The thickness of the metallic electrode 11 is set to an extremely
small thickness so that a mechanical resistance due to the metallic
electrode 11 can be suppressed to an excessively low level. Even
when a flexural oscillation is generated in the center of a uniting
plane (a part that does not expand and contract) of the two
ceramics elements 10a and 10b and the metallic electrode 11, the
damping of the flexural oscillation due to the metallic electrode
11 can be suppressed to a low level as much as possible. In the
structure of this embodiment, when the piezoelectric ceramics
element 10a of one side expands, the piezoelectric ceramics element
10b of the other side contracts and the electrodes of output
voltage are opposite each other. Thus, both the piezoelectric
ceramics elements 10a and 10b have a power generation structure in
which they are connected in parallel with each other.
Further, in this embodiment, when the above-described flexural
oscillation is generated, both the operations of expansion and
contraction are carried out in one piezoelectric ceramics element
10a (or 10b), power is efficiently generated without canceling the
polarization. Electric current as electric power energy generated
in the ceramics element 10a is taken out from a lead wire 9A.
Electric current as electric power energy generated in the ceramics
element 10b is taken out from a lead wire 9B. The electric current
generated respectively in the ceramics elements 10a and 10b is
connected to a lead wire 9C electrically connected to both the end
parts of the metallic electrode 11 to obtain alternating
current.
Here, a case that the two piezoelectric ceramics elements 10a and
10b are laminated through the metallic electrode 11 is described as
an example, however, each of the piezoelectric ceramics element 10a
(10b) itself may have a laminated structure. In this laminated
structure, a plurality of piezoelectric ceramics elements are
united together (in this case, the polarity of polarization is set
to the same direction) to form one piezoelectric ceramics element
10a (10b).
As described above, when the piezoelectric ceramics element 10a (or
10b) itself has the laminated structure and the plurality of
piezoelectric ceramics elements are united together by for
instance, an adhesive having elastic characteristics, the
piezoelectric ceramics member 10 low in its strength owing to its
material is easily bent due to an elastic effect. Thus, a flexural
strength of the piezoelectric ceramics member 10 can be maintained.
In the present invention, the outer form of the piezoelectric
ceramics member 10 is not limited to a special form. A suitable
form such as a circular form, an elliptic form, a triangular form,
a rectangular form or a polygonal form may be used in accordance
with a way of use.
Further, the cushion material 3 used in the present invention is
made of a synthetic resin material, a rubber material or a soft
material obtained by forming these materials in sponge. Only
central parts or both the ends of the cushion members 3 are fixed
to the piezoelectric ceramics members 10 by using the adhesives 5
not to damp the oscillation of the piezoelectric ceramics members
10. When the piezoelectric ceramics members 10 oscillate, members
for supporting the piezoelectric ceramics members 10 form factors
for damping the oscillation of the piezoelectric ceramics members
10. To remove the damping factors, the piezoelectric ceramics
members 10 are respectively brought into free states as much as
possible by using the cushion members 3.
As in the present invention, the distortion of the piezoelectric
ceramics members 10 forms a natural oscillation of the
piezoelectric ceramics itself and continues for a while. To
continuously keep this natural oscillation for a long time, it is
important not to transmit the natural oscillation to other
components except the piezoelectric ceramics members 10. The
natural oscillation of the piezoelectric ceramics members 10 is
converted to electric energy, however, the oscillation of other
structural members are all forms a mechanical resistance to absorb
natural oscillation energy so that the electric energy cannot be
taken out. Therefore, in this embodiment, as means for realizing a
soft contact that the natural oscillation is not transmitted
between the piezoelectric ceramics members 10 and other structural
members, the above-described cushion members 3 are used.
Accordingly, the natural oscillation of the piezoelectric ceramics
members 10 can be continued for a long time to improve power
generation efficiency. It is to be understood that the cushion
members 3 serve to mitigate an impact applied to the piezoelectric
ceramics members 10. The above-described protector plates 2 are
formed with metal, a synthetic resin or the like to protect the
piezoelectric ceramics members 10 from striking by the steel ball
4.
In this embodiment, as the striking member, the steel ball 4 is
arranged in the pipe 7 to strike the piezoelectric ceramics members
10. However, the material or the form of the striking member is not
limited to a ball made of steel and other cylindrical or egg-shaped
heavy materials may be used. Further, not only the striking member
is disposed in the pipe 7, but also the striking member may be
moved along a rail, as long as the striking member can freely move.
Further, a spring material (upward or downward) may be used in
place of the pipe 7, one end of the spring material may be fixed
and the steel ball 4 may be attached to the other end thereof so
that both the piezoelectric ceramics members 10 are struck in
accordance with the rightward and leftward oscillation of the
spring material.
When a piezoelectric power generation device according to this
embodiment constructed as described above is placed under an
environment of a prescribed moving state using wind, wave or an
artificial action, the steel 4 rolls in the pipe 7 to strike the
right and left piezoelectric ceramics members 10 and apply an
impact energy due to collision to the piezoelectric ceramics
members 10. Then, the piezoelectric ceramics members 10 are excited
to oscillate and repeatedly expands and contracts to generate AC
electric power. As a quantity of generated energy, what is called a
parallel type power generation device according to the present
invention, can obtain output current substantially twice as much as
a series type power generation device previously proposed by the
applicant of the present invention.
FIG. 2 shows a circuit of a charging device for electrifying the
electric power generated by one piezoelectric ceramics member 10 by
the use of the piezoelectric power generation device. In this
embodiment, because it is to be understood that the two
piezoelectric ceramics members 10 are opposed to each other, the
charging circuit is electrically connected in parallel with or in
series to the piezoelectric ceramics members. Further, the parallel
circuit shown in the drawing may be suitably increased to meet a
purpose of use.
Specifically, the charging circuit includes the two piezoelectric
ceramics elements 10a and 10b as the two piezoelectric ceramics
members 10, the metallic electrode 11, rectifier diodes D1 to D6, a
capacitor C for storing the electric power, a switch SW and light
emitting diodes L1 to L3. The electric power generated by the
piezoelectric ceramics element 10a is full-wave rectified by the
diodes D1 to D3. The electric power generated by the piezoelectric
ceramics element 10b is full-wave rectified by the diodes D4 to D6.
The capacitor C is charged with the full-wave rectified electric
power. The number of the capacitors C may be set to one in this
parallel circuit. Then, the capacitor C is discharged by operating
the switch SW to light the light emitting diodes L1 to L3.
FIG. 3 shows an ordinary structural example of the piezoelectric
ceramics member 10 used in the piezoelectric power generation
device constructed as described above. In this example, there is no
other method than a method that one end part of the metallic
electrode 11 interposed between the two piezoelectric ceramics
elements 10a and 10b protruding parts 11A outward from the other
end parts of the piezoelectric ceramics elements 10a and 10b and
the lead wire 9C is electrically connected to the protruding part
11A. However, when the protruding part 11A of the metallic
electrode 11 is projected outward from the other end parts of the
piezoelectric ceramics elements 10a and 10b as described above, the
protruding part 11A oscillates under a frequency different from the
distortion deformation of the piezoelectric ceramics elements 10a
and 10b. Thus, the oscillation of the protruding part 11A
interferes with the power generation of the piezoelectric ceramics
elements 10a and 10b so that an efficient power generation cannot
be realized.
Therefore, the protruding part 11A of the metallic electrode 11 may
be connected to the lead wire 9C, and then, effectively fixed by an
adhesive or the like.
In the present invention, as shown in FIGS. 4 and 5, one end parts
10a2 and 10b2 of the two piezoelectric ceramics elements 10a and
10b are aligned with a side 11B of the metallic electrode 11. In
this embodiment, the other end side 10b1 is formed to be longer
than the piezoelectric ceramics element 10a to form a step part
10b1. In this step part 10b1, the lead wire 9C is bonded and fixed
to the connecting end part 11A of the metallic electrode 11 (refer
this form to as an embodiment A, hereinafter). It is to be
understood that the other end part 10a1 of the piezoelectric
ceramics element 10a may be formed to be longer than the other end
part 10b1 of the piezoelectric ceramics element 10b to form a step
part, conversely to the embodiment shown in the drawings and the
lead wire 9C may be bonded and fixed to the connecting end part 11A
of the metallic electrode 11 in the step part 10a1 of the long
extended piezoelectric ceramics element 10 (refer this form to as
an embodiment B).
As described above, the metallic electrode 11 is supported by the
step part of the piezoelectric ceramics element 10a or 10b high in
its rigidity, so that the natural oscillation of the protruding
part 11A of the metallic electrode 11 can be prevented. Thus,
effective power generation efficiency can be obtained and the lead
wire 9C can be simply connected to the metallic electrode. In this
embodiment, the connecting end part 11A of the metallic electrode
11 is bonded and fixed to the step part as an example. However, the
present invention is not limited thereto and the connecting end
part may be deposited or plated.
FIGS. 6A and 6B show alternative examples of the above-described
embodiment A. In these examples, the connecting end part 11A
relative to the lead wire 9C has a small width necessary for
connection, which is different from the embodiment shown in FIGS. 4
and 5. Thus, factors that prevent an oscillation due to the
connecting end part 11A of the metallic electrode 11 are eliminated
as much as possible.
FIGS. 6C and 6D show alternative examples of the embodiment B.
These examples show that the connecting end part 11A relative to
the lead wire 9C has a small width necessary for connection, which
is different from the embodiment shown in FIGS. 4 and 5, so that
factors of preventing an oscillation due to the connecting end part
11A of the metallic electrode 11 are eliminated as much as
possible. According to the present invention, although there is not
especially shown in the drawings, it is to be understood the plane
and height dimensions of the piezoelectric ceramics element 10a or
10b may be formed to be equal, a cut-out part with a substantially
recessed form in plan view may be formed for connecting the lead
wire 9C in either the piezoelectric ceramics element 10a or 10b and
the electrode 11 may be exposed and connected to the cut-out
part.
The above-described charging device is used to form the parallel
type piezoelectric power generation device. Thus, the power
generation efficiency is improved to substantially twice as high as
the power generation efficiency obtained by a usual piezoelectric
power generation device. Accordingly, the power generation device
is effective as a power source for a charger or a light-emitting
device. Since the above-described power generation device has a
simple structure, can obtain a larger quantity of output current
and is economical, a more practical use may be anticipated. For
instance, when the piezoelectric power generation device is mounted
on a bicycle or shoes to light the light emitting diodes, the
piezoelectric power generation device can be used as a device for
allowing a presence to be recognized at night. Further, when the
piezoelectric power generation device is mounted on a battery type
wrist watch or a portable telephone, the power generation device
can be employed in place of a battery or a countermeasure for an
exhausted battery. Furthermore, the heaves of waves are used to
generate power, so that a use of a lighting device for a buoy can
be anticipated.
As described above, according to the present invention, in the
piezoelectric power generation device, the two plate shaped
piezoelectric ceramics elements are united together with the
polarization set to the same direction and the extremely thin
metallic electrode is interposed between the piezoelectric ceramics
elements to form the piezoelectric ceramics member in a laminated
shape. An impact load is applied to the piezoelectric ceramics
members to generate power. Thus, output current can be obtained
that is substantially twice as high as output current obtained in
the series type piezoelectric power generation device previously
proposed by the applicant of the present invention. Accordingly, an
applicable field can be greatly increased to improve
practicability.
Further, in the piezoelectric power generation device according to
the present invention, because the piezoelectric ceramics members
are supported by the cushion materials, the oscillation of the
piezoelectric ceramics members can be effectively continued for a
long time to improve the power generation efficiency.
Further, according to the present invention, because the
piezoelectric ceramics elements having the same configurations are
used to form the piezoelectric ceramics members in laminar shapes,
the piezoelectric ceramics elements properly expand and contact to
effectively more improve the power generation efficiency. Further,
according to the present invention, because each of the
piezoelectric ceramics elements is formed by uniting and laminating
a plurality of elements, the strength of the piezoelectric ceramics
elements can be effectively maintained.
Further, according to the present invention, a lead zirconate
titanate based material is used for the piezoelectric ceramics
elements to obtain a wide applicable range to the piezoelectric
power generation device and effectively realize a
practicability.
Further, according to the present invention, the metallic electrode
is made of electrically conductive metal such as phosphor bronze or
brass. The thickness of the metallic electrode is set to 10 .mu.m
to 50 .mu.m. Thus, even when the flexural oscillation of the
piezoelectric ceramics elements is generated to generate power, the
metallic electrode does not substantially exhibit a mechanical
resistance. Accordingly, the power generation efficiency is
effectively hardly reduced.
Further, according to the present invention, the two piezoelectric
ceramics elements are arranged uniformly in one end side, and, the
end part of one piezoelectric ceramics element is formed to be
longer than that of the other piezoelectric ceramics element in the
other side to form a step part, and a lead wire connecting end part
of the metallic electrode is extended and fixed to the step part.
Accordingly, since the metallic electrode can be supported by the
step part of the piezoelectric ceramics element high in its
rigidity, the parasitic resonance (natural oscillation) of the
protruding part of the metallic electrode can be prevented. At the
same time, more effective power generation efficiency can be
obtained and a connecting work of the lead wire to the metallic
electrode can be simply carried out.
Still further, according to the present invention, both the end
parts of the two piezoelectric ceramics elements are arranged
uniformly, the metallic electrode protrudes outward from one end
parts of both the piezoelectric ceramics elements, the lead wire is
connected to the protruding part, and then, the protruding part is
embedded in an adhesive to be formed integrally with the
piezoelectric ceramics elements. Thus, the natural oscillation of
the protruding part of the metallic electrode can be prevented,
more effective power generation efficiency can be obtained and the
lead wire can be simply connected to the metallic electrode.
* * * * *